Generally, in a compressor, particularly a reciprocating compressor, compression efficiency is higher than a general compressor since there is no crankshaft for converting a rotational movement into a linear movement, and thus a friction loss is small.
In case that the reciprocating compressor is used for a refrigerator or an air conditioner, as varying a stroke voltage applied to the reciprocating compressor (interior motor of the compressor), a compression ratio can be varied. For this reason, freezing capacity can be controlled. The operation controlling apparatus for the reciprocating compressor will now be described with reference to FIG. 1.
FIG. 1 is a block diagram showing a structure of an apparatus for controlling an operation of a reciprocating compressor according to a conventional art.
As shown therein, the apparatus for controlling an operation of the conventional reciprocating compressor includes a voltage detecting unit 14 for detecting a voltage applied to an interior motor 13 (illustrated as a coil of the interior motor) of the reciprocating compressor (not shown) when the reciprocating motor operates; a current detecting unit 12 for detecting a current applied to the motor (M) 13 when the reciprocating compressor operates; a microcomputer 15 for calculating a stroke of the compressor on the basis of a voltage value detected from the voltage detecting unit 14 and a current value detected from the current detecting unit 12, comparing the calculated stroke and a predetermined stroke reference value, and outputting a switching control signal on the basis of the comparison result; and a power supply unit 11 for supplying a stroke voltage to the motor 13 (M) by on-off controlling an interior triac (TR) according to the switching control signal outputted from the microcomputer 15. Herein, a resistor (R) of the power supply unit 11 is installed to detect a current applied to the motor 13 (M).
Operations of the apparatus for controlling an operation of the reciprocating compressor according to the conventional art will now be described.
First, the reciprocating motor receives a voltage supplied to the motor 13 depending on the stroke reference value set by a user, varies the stroke and vertically moves an interior piston. Herein, the stroke means a moving distance of the inner piston of the reciprocating compressor while the inner piston reciprocally moves.
A turn-on period of a triac of the power supply unit 11 is lengthened by a switching control signal outputted from the microcomputer 15. An alternating current power (stroke voltage) is supplied to the motor 13 due to the lengthened turn-on period, and thus the motor 13 is driven. At this time, the voltage detecting unit 14 and the current detecting unit 12 detect the voltage and the current applied to the motor 13 respectively, and output the detected voltage value and the current value to the microcomputer 15.
The microcomputer 15 calculates a stroke of the compressor on the basis of the voltage value detected by the voltage detecting unit 14 and the current value detected by the current detecting unit 12, then compares the stroke with the predetermined stroke reference value, and then outputs a switching control signal according to the comparing result. For example, when the calculated stroke is smaller than the predetermined stroke reference value, the microcomputer 15 outputs a switching control signal for lengthening a turn-on period of the triac to the power supply unit 11 and thus increases a stroke voltage supplied to the motor 13. On the other hand, when the calculated stroke is greater than the predetermined stroke reference value, the microcomputer 15 outputs a switching control signal for shortening a turn-on period of the triac to the power supply unit 11 and thus decreases a stroke voltage supplied to the motor 13.
However, when the apparatus for controlling the operation of the conventional reciprocating compressor is installed at a refrigerator and controls on-off of a triac, a high-priced digital signal processor (not shown) for controlling the triac is used, and thereby increasing costs for implementing the apparatus for controlling the operation of the reciprocating compressor.